CFD Validation of Scaled Floating Offshore Wind Turbine Rotor

Aerodynamic performance of a floating offshore wind turbine (FOWT) is significantly influenced by platform surging motions. Accurate prediction of the unsteady aerodynamic loads is imperative for determining the fatigue life, ultimate loads on key components such as FOWT rotor blades, gearbox and power converter. The current study examines the predictions of numerical codes by comparing with unsteady experimental results of a scaled floating wind turbine rotor. The influence of platform surge amplitude together with the tip speed ratio on the unsteady aerodynamic loading has been simulated through unsteady CFD. It is shown that the unsteady aerodynamic loads of FOWT are highly sensitive to the changes in frequency and amplitude of the platform motion. Also, the surging motion significantly influences the windmill operating state due to strong flow interaction between the rotating blades and generated blade-tip vortices. Almost in all frequencies and amplitudes, CFD, LR-BEM and LR-uBEM predictions of mean thrust shows a good correlation with experimental results.

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Multi-Fidelity Aerodynamic Modeling of a Floating Offshore Wind Turbine Rotor

Volume 10: Fluids Engineering ◽

10.1115/imece2020-24608 ◽

2020 ◽

Author(s):

Kai Zhang ◽

Onur Bilgen

Keyword(s):

Wind Turbine ◽

Turbine Rotor ◽

Modeling Method ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Blade Element Theory ◽

Momentum Theory ◽

Element Theory ◽

Wind Turbine Rotor ◽

Blade Element

Abstract This paper presents a comparison of low- and mid-fidelity aerodynamic modelling of floating offshore wind turbine rotors. The low-fidelity approach employs the conventional Blade Element Momentum theory implemented in AeroDyn of OpenFAST. This model ignores the aerodynamic interactions between different blade elements, and the forces on the blade are determined from the balance between momentum theory and blade element theory. With this method, it is possible to calculate the aerodynamic performance for different settings with low computational cost. For the mid-fidelity approach, the Actuator Line Modeling method implemented in turbinesFoam (an OpenFOAM library) is used. This method is built upon a combination of the blade element theory for modeling the blades, and a Navier-Stokes description of the wake flow field. Thus, it can capture the wake dynamics without resolving the detailed flows near the blades. The aerodynamic performance of the DTU 10 MW reference wind turbine rotor is studied using the two methods. The effects of wind speed, tip speed ratio, and blade pitch angles are assessed. Good agreement is observed between the two methods at low tip speed ratios, while the Actuator Line Modeling method predicts slightly higher power coefficients at high tip speed ratios. In addition, the ability of the Actuator Line Modeling Method to capture the wake dynamics of the rotor in an unsteady inflow is demonstrated. In the future, the multi-fidelity aerodynamic modules developed in this paper will be integrated with the hydro-kinematics and hydro-dynamics of a floating platform and a mooring system, to achieve a fully coupled framework for the analysis and design optimization of floating offshore wind turbines.

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Numerical Validation of Floating Offshore Wind Turbine Scaled Rotor for Surge Motion

10.20944/preprints201808.0484.v1 ◽

2018 ◽

Author(s):

Krishnamoorthi Sivalingam ◽

Steven Martin ◽

Abdulqadir Aziz Singapore Wala

Keyword(s):

Wind Turbine ◽

Turbine Rotor ◽

Power Converter ◽

Experimental Results ◽

Offshore Wind ◽

Speed Ratio ◽

Offshore Wind Turbine ◽

Floating Offshore Wind Turbine ◽

Aerodynamic Loads ◽

Unsteady Aerodynamic

Aerodynamic performance of a floating offshore wind turbine (FOWT) is significantly influenced by platform surging motions. Accurate prediction of the unsteady aerodynamic loads is imperative for determining the fatigue life, ultimate loads on key components such as FOWT rotor blades, gearbox and power converter. The current study examines the predictions of numerical codes by comparing with unsteady experimental results of a scaled floating wind turbine rotor. The influence of platform surge amplitude together with the tip speed ratio on the unsteady aerodynamic loading has been simulated through unsteady CFD. It is shown that the unsteady aerodynamic loads of FOWT are highly sensitive to the changes in frequency and amplitude of the platform motion. Also, the surging motion significantly influences the windmill operating state due to strong flow interaction between the rotating blades and generated blade-tip vortices. Almost in all frequencies and amplitudes, CFD, LR-BEM and LR-uBEM predictions of mean thrust shows a good correlation with experimental results.

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ALE–VMS formulation for stratified turbulent incompressible flows with applications

Mathematical Models and Methods in Applied Sciences ◽

10.1142/s0218202515400114 ◽

2015 ◽

Vol 25 (12) ◽

pp. 2349-2375 ◽

Cited By ~ 55

Author(s):

Y. Bazilevs ◽

A. Korobenko ◽

J. Yan ◽

A. Pal ◽

S. M. I. Gohari ◽

...

Keyword(s):

Wind Turbine ◽

Incompressible Flows ◽

Stable Stratification ◽

Turbine Rotor ◽

Multiscale Methods ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Moving Domains ◽

Thrust And Torque ◽

Wind Turbine Rotor

A numerical formulation for incompressible flows with stable stratification is developed using the framework of variational multiscale methods. In the proposed formulation, both density and temperature stratification are handled in a unified manner. The formulation is augmented with weakly-enforced essential boundary conditions and is suitable for applications involving moving domains, such as fluid–structure interaction. The methodology is tested using three numerical examples ranging from flow-physics benchmarks to a simulation of a full-scale offshore wind-turbine rotor spinning inside an atmospheric boundary layer. Good agreement is achieved with experimental and computational results reported by other researchers. The wind-turbine rotor simulation shows that flow stratification has a strong influence on the dynamic rotor thrust and torque loads.

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Effect of Platform Motion on Aerodynamic Performance and Aeroelastic Behavior of Floating Offshore Wind Turbine Blades

Energies ◽

10.3390/en12132519 ◽

2019 ◽

Vol 12 (13) ◽

pp. 2519 ◽

Cited By ~ 1

Author(s):

Kim ◽

Kwon

Keyword(s):

Wind Turbine ◽

Bending Moment ◽

Turbine Rotor ◽

Aerodynamic Performance ◽

Rotor Blades ◽

Offshore Wind ◽

Offshore Wind Turbine ◽

Floating Offshore Wind Turbine ◽

Platform Motion ◽

Aerodynamic Loads

In the present study, a numerical framework for predicting the aerodynamic performance and the aeroelastic behavior of floating offshore wind turbine rotor blades involving platform motion was developed. For this purpose, the aerodynamic and structural analyses were conducted simultaneously in a tightly coupled manner by exchanging the information about the aerodynamic loads and the elastic blade deformations at every time step. The elastic behavior of the turbine rotor blades was described by adopting a structural model based on the Euler-Bernoulli beam. The aerodynamic loads by the rotor blades were evaluated by adopting a blade element momentum theory. The numerical simulations were conducted when the platform of the wind turbine independently moves in each of the six degrees-of-freedom directions consisting of heave, sway, surge, roll, pitch, and yaw. It was observed that flexible blades exhibit complicated vibratory behaviors when they are excited by the aerodynamic, inertia, and gravitational forces simultaneously. It was found that the load variation caused by the platform surge or pitch motion has a significant influence on the flapwise and torsional deformations of the rotor blades. The torsional deformation mainly occurs in the nose-down direction, and results in a reduction of the aerodynamic loads. It was also found that the flapwise root bending moment is mainly influenced by the platform surge and pitch motions. On the other hand, the edgewise bending moment is mostly dictated by the gravitational force, but is not affected much by the platform motion.

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